Measuring glomerular filtration rate in children; can cystatin C replace established methods? A review

Our aim was to evaluate published methods that use serum cystatin C (s-CysC) for measuring glomerular filtration rate (GFR) in children and to discuss advantages and limitations of s-CysC and of established GFR methods. A comprehensive literature review of clinical studies in children evaluating s-CysC or CysC-based formulas and plasma creatinine or creatinine-based formulas against an exogenous reference method using receiver operating characteristics (ROC) curves or Bland-Altman plots is presented. The comparison of s-CysC with plasma creatinine indicated that s-CysC was superior to plasma creatinine in five of 13 studies; four studies showed no difference, and, in four studies, no statistical comparison was made. Comparison of s-CysC and the Schwartz formula showed that s-CysC was superior to the Schwartz formula in two of seven studies; two studies demonstrated no difference, and, in one study, the Schwartz formula was superior to s-CysC. In two studies no statistical comparison was made. The CysC-based prediction equations all had high accuracy but low agreement when compared with a reference GFR, in the range of 30-40% at best. S-CysC is most likely superior to plasma creatinine and at least equal to creatinine-based formulas. CysC-based prediction equations are at least as good as creatinine-based formulas but cannot replace exogenous methods.